I am so sorry that nobody has answered your post yet. Especially since you are in the middle of a nursing strike. First of all, a couple questions ... how often are you pumping? Do you nurse on one side only each time? Have you done any block feeding?
I understand the frustration and heartache you are going through, especially after having to give up nursing with your first child. Trust that you will be able to fix this problem and that your baby will be come to love nursing again. I've gone through many strikes with my little one. Be assured that your baby does WANT to nurse ... also know that he is not rejecting you, and that things will improve dramatically once you start working on the oversupply problem. I know how hard it is to have your little one in such distress when you try to nurse him.
My little girl started to associate nursing with the unpleasantness of the forceful let down and choking on the very rapid/copious flow of milk. Because I didn't know what was going on with her, she was eventually terrified to nurse period ... she would pull away before we even got to let down sometimes (or pull off when it let down, with milk spraying everywhere), or worse, (after we'd been going through this for a month) she would sometimes start crying as soon as I began to hold her in a nursing position. We had a major oversupply problem.
The number one thing that helped us get through our strikes was nursing her while she was sleepy or asleep. Also, side lying nursing as well as nursing on an incline to get gravity working in your favor. You can also let the milk spray into a towel when you let down, and then put baby back on afterwards.
For some reason it is usually around 3 months that our babies start to "complain" about it (that's when our problems surfaced too). This is info from LLL's The Breastfeeding Answer Book:
I found these resources very helpful, along with the advice of my local LLL Leader. Check these pages out ...
From three to six months of age, a baby who is having difficulty handling his mother's forceful let-down may refuse or postpone feedings. Even if nursing has gone fairly smoothly until this stage, some babies who have difficulty coping with the mother's forceful let-down may begin to exhibit a reluctance to nurse that may include some of the following symptoms:
-refusal to continue nursing when the mother switches breasts during a feeding
-refusal to nurse himself to sleep, preferring instead fingers, thumb, or a pacifier
-refusing some feedings even when obviously hungry
-"biting" the breast
-refusal to nurse at all (nursing strike)
My baby fusses or cries during nursing - what's the problem?
Forceful Let-down (Milk Ejection Reflex) & Oversupply
Am I making too much milk?
See this page for info on nursing strikes: Help -- My Baby Won't Nurse!
You also might find some really helpful info here on this thread: "Angry" Feedings / Puking - Help! I'm panicking!
I would highly recommend contacting a La Leche League leader or lactation consultant (IBCLC) for one-on-one support. They can guide you much better than anyone can over the computer.
Is there a La Leche League Group in your area? The leaders will help you for free. Here is the link to find one:
How to Find a La Leche League Leader Near You
There is also an excellent podcast LLL has about oversupply and overactive letdown. It's an MP3 file you can listen to. I also found this extremely helpful and informative ...
Oversupply of Breastmilk
LLL Leader Karen Smith talks with Elisabeth Lewin about identifying and overcoming the challenges of an oversupply of breastmilk, and/or of a forceful milk letdown (aka overactive milk ejection reflex). (29 min.)
You are doing a wonderful job hanging in there with your determination to breastfeed your little one. I promise things will get better and your baby will love to nurse again once you have a handle on the problem.